1. Field of Invention
The present invention relates to reduction of signal power loss in communications systems. The invention is more particularly related to the reduction of signal power loss in wireless RF systems. In addition, the invention relates to implementing antenna diversity in wireless systems.
2. Related Art
The use of multiple antennas has become a popular method of improving performance of wireless devices. A simple technique is called “switch diversity” in which a radio can alternatively transmit and receive through separate antennas using only one antenna at a time. The radio can decide which antenna to use based upon the success of previous communications. FIG. 1 is a diagram of a conventional, switch diversity architecture. A pair of antennas, Antenna A and Antenna B (diversity antennas 100), are located at diverse physical locations and/or are antennas having diverse physical properties (gain, directivity, etc.). The diversity antennas 100 are connected to a diversity switch 110 that connects the antennas to a transmit/receive switch 120. When transmitting, a baseband/mixers device 140 feeds a signal to a power amplifier (PA) 132 in RF front end 130. The transmit/receive switch 120 directs the amplified signal to the diversity switch 110, which in turn directs the amplified transmit signal to a selected one of the diversity antennas. When receiving a reverse signal flow occurs, except that the received signal is boosted by a low noise amplifier (LNA) 134 prior to being received by the baseband/mixers device 140.
The diversity switch 110 is controlled by software or other electronics that selects one of the diversity antennas for reception/transmission. Selection criteria are typically based on quality of signal, e.g. S/N ratio and/or other identifiers, such as packet reception errors, etc. For example, a typical arrangement would call for the baseband/mixers device 140 to include some processing or algorithm that activates a control signal to perform the switching. The processing could include receiving packets on each of the antennas for a length of time (or number of packets), and then comparing the number of packet errors received by each of the antennas. The antenna with the least number of errors or the highest S/N ratio could then be selected for broadcast/reception. Once an antenna is selected, transmission/reception continues on the selected antenna. Periodically, the other antenna(s) could be re-tested. In the event a re-test indicates an environment change or other factor is degrading performance of the selected antenna compared to the other antenna(s), the selected antenna is changed to the then best performing antenna.